Motors classification

NEMA motor classifications from Reference 31 for usual chemical and petrochemical applications are as indicated in Figure 14-3. 

There are a number of electric motor types available. These motors are classified by the National Electrical Manufacturers Association (NEMA). These electric motor classifications are presented in the NEMA standards [7]. 

The classification of motor oils has not been completed in the ISO standard because the technical differences between motors in different parts of the world, particularly Europe and the United States, make the implementation of a single system of classification and specifications very difficult. In practice, different systems coming from national or international organizations are used. The best known is the SAE viscosity classification from the Society of Automotive Engineers, developed in the United States. 

National Motor Freight Classfication 100-S National Classification Board, Washington, D.C., 1992. 

J. C. Colquitt, The Art and Development of Freight Classification, National Motor Freight Traffic Association, Inc., Washiagton, D.C., 1956. 

Uniform Freight Classification Committee, Rules 40 and 41 American Bureau of Shipping National Cargo Bureau National Motor Freight Traffic Association National Motor Freight Classification National Fire Protection Association... 

In drawing contracts and making acceptance tests, refer to the pertinent ASTM standards. ASTM Standards contain specifications (classifications) and test methods for burner fuels (D 396), motor and aviation gasolines (D 4814 and D 910), diesel fuels (D 975), and avia-... 

Except for areas with fire or explosion hazards (hazardous areas), motor enclosures are designed to provide protection to the internal working parts. The development or improved insiilating materials and finishes has affec ted the required degree of protection and consequently the design and classification of enclosures. Examples of several types of enclosures are shown in Fig. 29-4. 

Selection of gapless surge arrester Classification of arresters Surge protection of motors Pressure relief facility Assessing the condition of an arrester... 

The selection of the motor enclosure type involves not only economics but also assessment of two factors area hazard classification and other area operation conditions. 

The compressor or blower installation in a typical refinery or chemical process unit is not out-of-doors completely. Some form of shelter often is provided, ranging from only a roof to a completely closed building. When process equipment such as a centrifugal gas compressor, which is not hazardous in normal operation, is present in the shelter, the hazard classification depends on the extent to that which the shelter restricts ventilation. The extent of the shelter provided determines the area classification and the type of motor enclosure that should be applied. 

In Division 1 areas, motors and generators must be either explosion-proof or approv ed for the classification by meeting specific requirements for a special ventilation system, inert gas-filled construction, or a special submerged unit. Although explosion-proof motors are expensive, they normally are available. Explosion-proof generators normally are not available. 

It is important, especially when consistency has not been designed or built into the maintenance reporting system, to review the data reported to minimize misinterpretation. Clearly defined equipment boundaries for plant hardware are essential for the generation of relevant data. For example, one classification method may define pumps as only the mechanical portions of the pump, whereas another may include the driver (e.g., the motor) and associated controls. Interviews with operating and maintenance personnel as well as review of the maintenance procedures and documents can provide insight into the... 

After an area classification has been established, then anelectrical equipment, instruments, and wiring must adhere to that classification. Therefore, some motor enclosure types would not be electrically acceptable for specific area classifications. 

Table 14-1 IB is useful in comparing motor temperature rise versus class of insulation. See section NEMA MG-1, Rev. 1, Part 1, Section 1, p. 15, Classification of Insulation Systems. ...

Energy Efficient (EE) Motor Designs, 628 NEMA Design Classifications, 630 Classification According to Size, 630 Hazard Classifications Fire and Explosion, 631 Electrical Classification for Safety in Plant Layout, 647 Motor Enclosures, 649 ... 

Figure 3-8 shows a graphic breakdown of the various electric motors available [8]. The outline in Figure 3-8 is based on an electrical classification. Besides their classification, NEM.A also classified electric motors according to... 

Motor enclosures for outdoor use are NEMA weather-protected Type II, totally enclosed, fan-cooled, or drip-proof with weather protection. Motors of the latter type are widely used. Not only are they less expensive than the other types, but they also have a service factor of 1,15. The above enclosure types are all suitable for the Class I, Group D, Division 2 classifications usually encountered. 

If the pumps are located indoors, a Division 1 classification is likely to apply. Motors must be Class 1, group D, explosion-proof, or they may be separately ventilated with clean outside air brought to the motor by fans. Auxiliary devices such as alarm contacts on the motor must be suitable for the area classification. The installed costs, overall efficiencies, and service factors associated with the enclosures that are available will influence the selection. 

Figure 51.3 provides an example of a typical work breakdown stmcture. The major divisions define specific, logical task groupings as well as the cost-accounting classifications. In the example, cost should be acquired for the preparation of the foundation, installation and final com-misioning of the pump and motor. In addition, each of the sub-tasks that comprise these classifications are logical groups of tasks that must be completed in sequence and by different work classifications. 

What electrical classification would be specified for an area that has Classes I and II, Groups A and E, and Divisions 1 and 2 motors ... 

Motors, electrical components, and electrical installations shall be suitable for the area classification (class, group, division, or zone) specified by the purchaser and shall meet the requirements of local codes (such as NFPA 70, Articles 500,501, and 502) specified by the purchaser. 

Anatomical differences between the peripheral somatic and autonomic nervous systems have led to their classification as separate divisions of the nervous system. These differences are shown in Figure 9.1. The axon of a somatic motor neuron leaves the CNS and travels without interruption to the innervated effector cell. In contrast, two neurons are required to connect the CNS and a visceral effector cell of the autonomic nervous system. The first neuron in this sequence is called the preganglionic neuron. The second neuron, whose cell body is within the ganglion, travels to the visceral effector cell it is called the postganglionic neuron. 

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